Localization of brain 5α-reductase messenger RNA in mice selectively bred for high chronic alcohol withdrawal severity.

Several lines of evidence suggest that fluctuations in endogenous levels of the γ-aminobutyric acid (GABA)ergic neurosteroid allopregnanolone (ALLO) represent one mechanism for regulation of GABAergic inhibitory tone in the brain, with an ultimate impact on behavior. Consistent with this idea, there was an inverse relationship between ALLO levels and symptoms of anxiety and depression in humans and convulsive activity in rodents during alcohol withdrawal. Our recent studies examined the activity and expression of 5α-reductase (Srd5a1), the rate-limiting enzyme in the biosynthesis of ALLO, during alcohol withdrawal in mice selectively bred for high chronic alcohol withdrawal (Withdrawal Seizure-Prone [WSP]) and found that Srd5a1 was downregulated in the cortex and hippocampus over the time course of dependence and withdrawal. The purpose of the present studies was to extend these findings and more discretely map the regions of Srd5a1 expression in mouse brain using radioactive in situ hybridization in WSP mice that were ethanol naïve, following exposure to 72h ethanol vapor (dependent) or during peak withdrawal. In naïve animals, expression of Srd5a1 was widely distributed throughout the mouse brain, with highest expression in specific regions of the cerebral cortex, hippocampus, thalamus, hypothalamus, and amygdala. In dependent animals and during withdrawal, there was no change in Srd5a1 expression in cortex or hippocampus, which differed from our recent findings in dissected tissues. These results suggest that local Srd5a1 mRNA expression in WSP brain may not change in parallel with local ALLO content or withdrawal severity.

Gaussian-beam mode analysis of reflection and transmission in multilayer dielectrics.

The analysis of reflections from thin films or dielectric materials can be approached by a matrix method that treats any thin-layer device as a cascade of sequential, zero-thickness reflecting thin-layer surfaces [J. Opt. Soc. Am. A2, 1363 (1985)]. Our paper presents an alternative method for predicting the reflection/transmission characteristics of such dielectric films in a Fabry-Perot interferometer configuration based on a Gaussian-beam modal analysis within a scattering-matrix framework [in Proceedings of IEE 7th International Conference on Antennas and Propagation (IEE, 1991), Issue 15, p. 201.] We present and validate a scalar Gaussian-beam modal scattering-matrix approach using long-wavelength examples, where diffraction effects are important to model total transmission and reflection characteristics that also include a waveguide modal description of a corrugated horn. For optical beams the same technique is equally applicable, but diffraction is less severe within this framework. This approach is flexible and has many applications within laser optics and in far-infrared or submillimeter-instrumentation optical analysis, where it is possible to incorporate reflections in both waveguide and free space within the description of a whole system. To conclude and verify the accuracy of the technique, experimental measurements taken at 94 GHz are compared with theoretical predictions for a dielectric cavity of polyethylene sheets between corrugated source and detector antennas.